E.were not eager at investing the new money, instead preferring to raise the cash levels in their portfolios to
别的问题都不大，知道答案选B，但是想问一下这里的prefering做的是什么角色？是纯粹的和instead构成一个固定用法，还是做adverbial modifer修饰前句？
另外对时态的理解我是这样理解的：
At least, when it comes to tense, it’s better to keep one tense in the same sentence, if there is no apparent signal to change the tense. Here, there is no signal in the sentence to choose the past tense because the only time signal at the end of the sentence refers to future. So it’s better to choose present perfect.
不知道对不对？还是对现在完成时的选择有点不太清楚。